The present invention relates to a planar color light emitting device which is used as a backlight for a liquid crystal or the like.
As a backlight for a liquid crystal or the like there is known a planar color light emitting device which uses light sources of three primary colors (red, green and blue) (see Japanese Patent Application Laid-Open Publication No. Hei 6-138459). This planar color light emitting device comprises a casing having an inner surface formed using a reflecting mirror surface and light sources of three primary colors (red, green and blue) disposed side by side within the casing.
However, in the above-described conventional technique, the light emitted from the light source disposed close to a side surface portion of the casing is reflected by a bottom surface portion of the casing and is also reflected in a considerable amount by the side surface portion toward an obverse surface side. For this reason, as a result, it appears that the luminance of the light source located at a terminal end is higher than the luminance of the light source located at a central part of the casing.
Accordingly, at the central part of the casing the luminances of the respective light sources are kept uniformly balanced, whereas in the proximity of the side surface portion of the casing the luminance of the color located at the terminal end is so high that the balance in luminance between this color and another color becomes non-uniform. For example, when simultaneously causing the light sources of the three primary colors to emit light in order to obtain "a white color", the central part of the luminous surface exhibits the white color but, in a case where the terminal light source is blue, the blue color becomes intense in the vicinity thereof. And, in a case where the light source disposed at the terminal end is red, the red color becomes intense in the vicinity thereof. For this reason, it is difficult to obtain a complete white color over an entire luminous surface.
The above-described inconvenience is mitigated by hiding the side surface portion and its vicinity where color unevenness occur by means of a frame or the like. However, in such a structure, the area of the actually usable luminous surface becomes narrowed compared to the size of the planar color light emitting device as a whole.